Our study plan is as follows: a) Analysis of the gamma-amino butyric acid (GABA) and beta-alanine contents of aqueous humor. b) Based on the above findings (as in a), a "physiological" corneal endothelial perfusion fluid is to be formulated which, in addition to the basic salts, will contain the following organic materials: glucose, insulin and beta-alanine or GABA. c) We plan to determine the suitability of the rabbit corneal endothelial preparation as a screen for GABA mimetic agents or GABA antagonists.